In 3, if you wanted to build a two sides free way with overpasses and tunnels, be prepared for a janky mess of two inevenly spaced roads and bridges with basic roads comming off them right at a 90% angle to a freeway (highway for Americans).
I think in 4 aswell as controlling width, you should have an option menu for each road segment, roads wouldn’t be placed by “nodes” as such, but would be placed similar to city building games like city skylines. Like in city skylines placing roads into each other would create an intersection automatically, things like dirt roads won’t create an intersection automaticity.
Bridges
Bridges would be built under the same tab as roads, the road segments will be linked and not jammed into each other like right now in 3. They could curve and work there way around buildings, making the large city’s have many connecting overpasses. A height option would be available for each segment, you could control how fast the bridge rises, and any heigh changes.
Town Roads
All roads would have customisable settings and could have a snap with worlds grid option, that eliminates the need for “road line” objects to keep your roads in city’s looking clean, you could have different angled intersections and have a complex city that has curves and bends, not all 90 degree turns. All these roads could have their settings changed, so some roads would be bigger than others and link up to smaller roads with ease, in real city’s roads are all different sizes and connect fine, and not using some ugly trick to join them up Plus there would still be presets and types for ease.
These roads will be able to connect in many more ways. For leaving a freeway insteed of just having a road off, you could change the settings so that an extra lane is added for that segment that has another road split off it. You could control colour, lanes, intersection and connections and much more.
Tunnels
Tunnels can be built easily aswell, you would select the tunnel option and select the depth it would start at as you dragged it around.
For building freeways aswell, you would be able to select multiple roads and move them together, so they stay neat.
Trains
This compatibly would also do wonders for trains, the roads would be reconised by the computer as connected, and trains could actually change lines instead of being stuck to one rout.
, seriously though this is a good idea 